Four people have died in the Midwest as records were set in the Chicago Botanic Garden (minus 3 degrees Fahrenheit ) and Cook County, Minn. (minus 34 degrees Fahrenheit), according to The New York Times.

The National Oceanic and Atmospheric Administration (NOAA) notes there is a daily cycle of heating and cooling, "but the pattern is clear: much of the U.S. is pretty cold."

This video from the NOAA shows the wave of Arctic air that's caused temperatures to fall dramatically. Areas colored blue are below freezing.